A fluorometric immunoassay is described for the determination of patulin, a highly toxic fungal metabolite. A rabbit anti-patulin-bovine serum albumin (BSA) IgG conjugate was prepared and used to compose immunoliposomes and immunomagnetic nanoparticles. The immunomagnetic nanoparticles are then added to the sample to form the patulin-antibody composites which can be magnetically separated. The immunoliposomes are then added to form a sandwich. After magnetic separation of the composites and adding n-octyl-β-D-glucopyranoside, the fluorophore sulforhodamine B (SRB) is released. Its fluorescence intensity was then measured at excitation/emission wavelengths of 550/585 nm. The immunoliposome-based immunomagnetic nanoparticle assay can detect 8 μg L-1 of patulin in apple juice without the need for extraction, separation, and purification. The detection limit falls within the European regulatory limit for infants and children's products (10 μg L-1). The method is rapid, enviroment-friendly, and reliable. Graphical abstractSchematic of the immunoassay.An immunoliposome-patulin-immunomagnetic nanoparticle sandwich complex is formed that can be separated from the sample by magnetic force. The fluorescence of sulforhodamine B carried inside of immunoliposome was measured to determine patulin. The method can detect 8 μg L-1 of patulin in apple juice.
Keywords: Apple juice analysis; Fluorescence intensity; HPLC; Patulin; Rapid detection.